Field of the Invention
This invention relates to a cleaning device for use in an electrophotographic copying machine. More particularly, the invention relates to a cleaning blade for removing charged powders adhering to the surface of a photosensitive member which is repeatedly used.
Various methods of forming static latent images have been proposed in electrophotography. For instance, there is a method comprising forming a photosensitive layer on a carrier, applying a static charge on the photosensitive layer by corona discharge in a dark place, and exposing an original to light while holding the original closely to the photosensitive layer or by projecting the original onto the photosensitive layer by means of an optical system, to thereby obtain a static latent image corresponding to the original. In order to visualize or develop this static latent image, charged toner powder is applied thereto. The development method may be the cascade development method, the magnetic brush development method, the powder cloud method or the like. In an electrophotographic copying machine of the type where the photosensitive layer is used repeatedly, the image is generally transferred onto copy paper by static transfer, roll transfer, adhesion transfer or the like. During this step, the charged powder (hereinafter referred to as "toner") is almost completely transferred onto the copy paper; however, a very small portion is left on the photosensitive layer. Since the photosensitive layer is used repeatedly, this remaining toner must be removed therefrom. For this purpose, a cleaning brush, a web, a blade or the like is usually employed. The image transferred onto the copy paper is fixed by heat treatment or by a heat roll or with an organic solvent.
The foregoing cleaning methods are unsatisfactory in some respects. More specifically, if a cleaning brush is used, hairs of an artificial or natural fiber such as rayon or Dynel are planted on the surface of a cylinder, and this cylinder is rotated, if necessary. Application of a static charge to the brush and the simultaneous action of a suction blower sucks the toner from the photosensitive layer where it is recovered in a filter bag. This method is employed quite broadly. However, since the cleaning mechanism includes a suction blower, a filter bag, a brush and the like, it is quite large. Accordingly, it fails to meet demands generally required in an office machine. Namely, it fails to meet the requirements of small size, economical cost and ease of maintenance. Further, the recovered toner is not suitable for repeated use, because a large amount of brush hair and the like is incorporated in the recovered toner.
A cleaning web is also utilized in the art. According to this method, the size of the cleaning mechanism can be made relatively small. However, a considerable amount of cleaning web paper or cloth is used. Further, it is difficult to discard the waste paper and replacement of the web occurs frequently.
A method for overcoming the above problems comprises contacting a rubbery sheet blade with the surface of the photosensitive member to thereby remove the toner remaining on the surface.